This invention relates to expandable tubing for a well bore hole and the method for expanding the tubing within the bore hole.
Heretofore, expandable tubing has been utilized in a bore hole particularly as a liner for both a cased hole section of a well bore and an uncased hole section of a bore hole. The liner is normally expanded until it contacts the bore wall which is formed by the adjacent formation or a casing. A mandrel of a diameter greater than the internal diameter of the expandable tube is normally used for radial expansion of the tubing.
The tubing may be slotted to assist in expansion and expandable slotted tubing (EST), (as shown in U.S. Pat. No. 5,366,012 dated Nov. 22, 1994), may be used in various downhole applications. The tubing comprises lengths of tube which have been machined to create a large number of axial extending elongate slots arranged in an overlapping relation. Thus, it is relatively easy to expand the tube radially outwardly by, for example, running a mandrel through the tubing. The expansion causes the axially extending overlapping elongate slots to extend to create diamond-shaped apertures. The tubing is useful where it is desired to, for example, line a bore below a restriction without further reducing the diameter of the bore. Using conventional tubing the outer diameter of the tubing must, by necessity, be of smaller diameter than the restriction, to permit the tubing to be passed through the restriction. This reduction in the bore diameter has a number of significant effects, primarily in reducing the production capabilities of the bore. Using EST, the tubing may pass through a restriction into a reamed section of bore below the restriction. The tubing may then be expanded to a diameter larger than the restriction.
EST is supplied in lengths which are, at present, made up into a string by welding the lengths to one another. This is relatively time consuming and expensive and in may situations, for example in an off-shore operation in bad weather, it may be difficult to maintain consistent weld quality. Safety problems may also arise due to the high temperatures and exposed flames or sparks created by a welding operation. Further, in the event of a xe2x80x9cmis-runxe2x80x9d, requiring the welded lengths of tube forming the EST string to be separated, the tubing must be cut, and the cut tubing may not be suitable for re-use.
As described in International Publication No. W096/37680 published Nov. 28, 1996; a connector assembly for interconnecting sections of an expandable slotted tubing string is provided with connected parts being slotted to permit expansion of the coupled parts.
As used herein, the term xe2x80x9cslottedxe2x80x9d or xe2x80x9cslotsxe2x80x9d is interpreted as including any cutting, machining or weakening of a tubular structure intended to facilitate radial expansion, including, but not limited to: openings, elongate slots, indentations, marks or slits which extend through or partially through the tube wall and which permit the remaining thinned wall sections to fracture or extend; holes which extend through the tube wall including drilled openings in various patterns such as tapered frusto-conical openings; and reduced thickness wall portions. The term xe2x80x9ctubexe2x80x9d or xe2x80x9ctubingxe2x80x9d is interpreted as including coiled tubing and jointed tubular sections.
However, heretofore, there has been no tailoring of slots for a predetermined bore hole length portion and only a single slot pattern for tubing has been provided heretofore. Thus, the most desirable slot pattern for a particular bore hole length may not be obtained. The bore hole may include various length portions for expandable tubing which require different expansion characteristics for the expandable tubing when transversely aligned with predetermined bore hole length portions.
It is an object of this invention to provide expandable tubing having length portions with different predetermined expansion characteristics so that transversely aligned bore hole length portions having different diameters resulting particularly from collapsing obtain the desired radial expansion from the adjacent transversely aligned slotted tubing.
Another object is to provide tubing for a well bore hole with the tubing having predetermined weakened length portions thereof with different predetermined radial expansion characteristics for different length portions of the well bore hole.
A further object is to provide a tubing for an open bore hole having expandable slotted length portions for the injection of fluids for isolation of a zone.
A further object is the provision of a method for inserting and expanding tubing within a bore hole and including longitudinally spaced length portions of the tube with different predetermined slot configurations for expansion to predetermined radial diameter conforming to adjacent diameter portions of the bore hole.
The present invention is particularly directed to a system for expandable slotted tubing (EST) for a bore hole in which predetermined length portions of the tubing are provided with different slot patterns or configuration tailored for a corresponding bore hole length portion when transversely aligned with the corresponding bore hole length portions. For example, the bore hole length portion in a gas zone may require a slot configuration for a transversely aligned length portion of the expandable slotted tube different from the slot configuration in a length portion of the expandable slotted tube against an oil bearing or said producing zone of the bore hole. Also, for example, a slot configuration for the EST particularly adapted for receiving a polymer gel or other material which is injected through the EST in the formation adjacent the EST for isolating or fracturing the adjacent formation. The slot pattern or configuration for a predetermined length portion of the expandable slotted tube may be practically endless and various configurations of slits, slots, holes, and weakened portions, for example, may be utilized. The slot pattern for a predetermined length portion is determined by the particular expansion characteristics desired for the corresponding bore hole length portion.
The present invention is also directed to the plastic deformation of weakened length portions of tubing with various configurations for the weakened length portions tailored for a predetermined transversely aligned bore hole length. Nonlinear finite element analysis (FEA) has been performed on various slots including circular holes and elongate slot configurations for providing the weakened portion of the tubing at predetermined length portions thereof.
The term xe2x80x9cslotxe2x80x9d or xe2x80x9cslotsxe2x80x9d as interpreted above includes circular holes, tapered frusto-conical openings, elongate slots, and slits in addition to other weakening elements for the expandable tubing as interpreted above. In some predetermined length portions of the tubing, the length portions are not weakened in any manner and in some instances, the major length of the tubing may not be weakened. Circular openings and elongate slots arranged in a non-overlapping angular relation to each of about 45 degrees have been found to be preferable for weakening predetermined length portion of the tubing.
The predetermined pattern for predetermined weakened length portions along the length of the tubing may be created on a strip material with the strip then being rolled and welded. Expansion of the predetermined length portion of the tubing may be achieved, for example, by pressurized fluid or gas, mechanical expansion tools utilizing hydraulic fluid, or explosives.
Normally, a caliber survey of the well bore is performed to determine the design requirements for the weakened portions of the tubing.
Other features and advantages of the invention will become more apparent from the following specification and drawings.